Thread: .303 reloads

Using a smaller charge of fast powder in a larger case can cause serious pressure issues, as the powder lays flat exposing a larger than normal surface area so it can ignite in mass not progressivly and cause a massive pressure spike. It is not safe to transfer load data from one case to another as the dynamics of ignition are case size dependent.[/QUOTE]

You have it wrong it is small amounts of SLOW burning powder that is supposed to cause Secondary Explosive Effect it has never been done in lab tests so is concidered an urban myth, Though it will happen with a double charge
of FAST burning powder,
it you want plinking loads use Trail Boss 70% fill the case and you are good to go, 27.0 Grains of 2206H is a favourite light load in the .303 and .308 with cast bullets and should work with jacketed work down to it rather than up
Start at 40.0 grains and go down .5 grain at a time.